I have a sketch where I use the BWoD methodology to fade a single LED. There is a lot of extra code, but it might help to see how I have all the different bits interleaved together. (I even have the fade on rate different than the fade off rate, look carefully to see how I did that.)
/*
* Entry Sensor Light: with Sharp Distance Sensor and PWM Output
* - Use a distance sensor (Sharp# GP2Y0A710K0F) to fade a PWM output up when
* the sensed distance changes. Then after a time out, fade the PWM output
* down at a (potentially) different rate.
*
* By Chris "Sembazuru" Elliott, SembazuruCDE (at) GMail.com
* 2013/10/28
*
* To the extent possible under law, Chris "Sembazuru" Elliott has waived all
* copyright and related or neighboring rights to SharpDistanceSensorPWMout.ino
* See http://creativecommons.org/publicdomain/zero/1.0/ for details.
* (Attribution would be nice, but in no way compulsory.)
*
* Hardware configuration on Arduino UNO:
* - Analog output of sensor to A0
* - LED13 used to show trigger status
* - PWM on pin 3 used for the fading output (pin 4 used as ground reference for
* testing with 0.1" 5V LED)
* - A5 pin used to disable serial diagnostics (A4 pin used as ground reference
* for testing with 0.1" shorting pins)
*/
// See http://playground.arduino.cc/Main/runningMedian for details and downloads.
#include <RunningMedian.h>
// Pair of pins to enable serial diagnostics. Short these two pins (or just the diagnosticsPin to ground) to silence serial diagnostics.
const byte diagnosticsPin = A5;
const byte diagnosticsGnd = A4;
boolean startDiagnostics = true;
// Constants and variables for data collection.
const byte sensorPin = A0;
unsigned int currentADC;
float currentAverage;
const byte medianArraySize = 19; // number of data points to collect to calculate the average (class range is 5-19)
const byte medianAverageSize = 9; // number of data points to average in the middle of the sorted median array to get an average reading while ignoring outliers
const unsigned long readingInterval = 17; // Sensor readings take 16.5ms +/- 3.7ms.
unsigned long readingStart = millis();
RunningMedian myMedian = RunningMedian(medianArraySize);
// Constants and variables for triggering.
const unsigned int PAcnt = 5; // highest index number for the array holding previous values. Number of previous values will be this plus 2 because array indexes start counting at 0, not 1 and comparison is based on the overflow value.
float previousAverages[PAcnt + 1]; // holding array for previous values to be used as a small pipe
float lastSignificantAverage = 0; // will recieve the previousAverages pipe overflow and be used in the trigger comparison
const unsigned int triggerThreshold = 5; // +/- value for average deltas to indicate if a trigger should happen
const byte triggerLED = 13; // Indicator LED for trigger
const unsigned long triggerDelay = 10000; // How long the trigger will last (minimum) in milliseconds
unsigned long triggerStart; // To allow capturing the time at the start of a trigger
boolean triggered = false; // flag for trigger state
// Constants and variables for fading the output up and down.
boolean fading = false; // true == need to fade, false == done fading.
boolean fadeDir = false; // true == up, false == down.
const byte fadePin = 3; // PWM pin to fade up and down.
const byte fadeGnd = 4; // Adjacent ground provided for use of 0.1" spacing 5V LED.
const int fadeMin = 0;
const int fadeMax = 255;
const byte fadeStep = 4; // How much to change the fadeValue by each iteration.
const byte fadeUDRatio = 2; // Amount to divide the fadeStep by when fading down to change the fade up to fade down rate ratio.
const unsigned long fadeTime = 3000; // How many milliseconds (base) to take for the fade up.
const unsigned long fadeStepInterval = fadeTime / ((fadeMax - fadeMin) / fadeStep); // Calculate how long between fade steps. Do this calculation once here.
unsigned long fadeStepStart = millis();
int fadeValue = fadeMin;
void setup()
{
Serial.begin(115200);
while (!Serial); // Wait for serial port to connect. Needed for Leonardo only.
delay(1000); // Simply to allow time for the ERW versions of the IDE time to automagically open the Serial Monitor. 1 second chosen arbitrarily.
// Setup pins for enabling/disabling serial diagnostics.
pinMode(diagnosticsGnd, OUTPUT);
digitalWrite(diagnosticsGnd, LOW);
pinMode(diagnosticsPin, INPUT_PULLUP);
// Setup pins for using the onboard LED to indicate triggering.
pinMode(triggerLED, OUTPUT);
digitalWrite(triggerLED, LOW);
// Setup pins for the fading (fading) PWM pin.
pinMode(fadeGnd, OUTPUT);
digitalWrite(fadeGnd, LOW);
analogWrite(fadePin, fadeValue);
// Initialize previousAvereages array here because it broke above.
for (int i = 0; i < PAcnt; i++)
{
previousAverages[i] = 0; // Zero it out. Don't want undefined values mucking about.
}
}
void loop()
{
if ((millis() - readingStart) > readingInterval)
{
getData();
triggerCheck();
diagnostics(readingStart);
}
if (fading)
{
if ((millis() - fadeStepStart) > fadeStepInterval)
{
fadeValue = fadeOutput(fadeValue, fadeStep, fadeDir);
diagnostics(fadeStepStart);
}
}
}
void getData()
{
do
{
readingStart = millis();
currentADC = analogRead(sensorPin);
myMedian.add(currentADC);
lastSignificantAverage = previousAverages[PAcnt]; // grab the last value as overflow
for (int i = PAcnt; i > 0; i--)
{
previousAverages[i] = previousAverages[i - 1]; // shift all the values up one spot in the array
}
previousAverages[0] = currentAverage; // put the previous average in the beginning of the array
currentAverage = myMedian.getAverage(medianAverageSize); // get the new average
}
while (myMedian.getCount() < myMedian.getSize()); // If the array isn't full loop back and take another reading.
}
void triggerCheck()
{
// Trigger if the median drops by more than the threshold or raises by more than the threshold.
if ((currentAverage < (lastSignificantAverage - triggerThreshold)) || (currentAverage > (lastSignificantAverage + triggerThreshold)))
{
triggerStart = millis();
triggered = true;
fading = true; // Start (or continue) fading...
fadeDir = true; // ...up
digitalWrite(triggerLED, HIGH);
}
// If currently triggered, check to see if enough time has passed since the last trigger event to turn off the trigger.
if (triggered)
{
if ((millis() - triggerStart) > triggerDelay)
{
triggered = false;
fading = true; // Start (or continue) fading...
fadeDir = false; // ...down
digitalWrite(triggerLED, LOW);
}
}
}
int fadeOutput(int _value, int _step, boolean _dir)
{
fadeStepStart = millis();
if (!_dir) // if down...
{
_step = -_step / fadeUDRatio; // ...set step direction negative and scale the rate
}
_value += _step;
if (_value < fadeMin)
{
_value = fadeMin;
fading = false;
}
if (_value > fadeMax)
{
_value = fadeMax;
fading = false;
}
analogWrite(fadePin, _value);
return _value;
}
void diagnostics(unsigned long _time)
{
char _comma[] = ",";
if (!digitalRead(diagnosticsPin)) // Check the diagnostic pin, only send out diagnostics if the pin is high.
{
startDiagnostics = true; // re-enable the header line for output
return;
}
if (startDiagnostics)
{
// Use the F() macro throughout to not waste valueable SRAM on diagnostic messages.
startDiagnostics = false;
Serial.print(F("\"Time\""));
Serial.print(_comma);
Serial.print(F("\"myMedian.getCount()\""));
Serial.print(_comma);
Serial.print(F("\"currentADC\""));
Serial.print(_comma);
Serial.print(F("\"currentAverage\""));
Serial.print(_comma);
Serial.print(F("\"lastSignificantAverage\""));
Serial.print(_comma);
Serial.print(F("\"deltaAverage\""));
Serial.print(_comma);
Serial.print(F("\"triggered\""));
Serial.print(_comma);
Serial.print(F("\"fading\""));
Serial.print(_comma);
Serial.print(F("\"fadeDir\""));
Serial.print(_comma);
Serial.print(F("\"fadeValue\""));
Serial.println();
}
Serial.print(_time);
Serial.print(_comma);
Serial.print(myMedian.getCount());
Serial.print(_comma);
Serial.print(currentADC);
Serial.print(_comma);
Serial.print(currentAverage);
Serial.print(_comma);
Serial.print(lastSignificantAverage);
Serial.print(_comma);
Serial.print(currentAverage - lastSignificantAverage);
Serial.print(_comma);
Serial.print(triggered);
Serial.print(_comma);
Serial.print(fading);
Serial.print(_comma);
Serial.print(fadeDir);
Serial.print(_comma);
Serial.print(fadeValue);
Serial.println();
}
Hope this helps more than confuses. 